1. Technical Field
The present invention relates to a liquid flow-path member that forms a liquid flow path of a liquid ejecting head such as an ink jet-type recording head, a liquid ejecting head that includes the liquid flow-path member, and a liquid ejecting apparatus that includes the liquid ejecting head, and particularly to the liquid flow-path member, the liquid ejecting head, and the liquid ejecting apparatus in which substrates that configure the liquid flow-path member are joined to each other by an adhesive.
2. Related Art
A liquid ejecting apparatus includes a liquid ejecting head and ejects various liquids from the ejecting head. An example of the liquid ejecting apparatus includes an image recording apparatus such as an ink jet-type printer or an ink jet-type plotter. Recently, the liquid ejecting apparatus is also applied to various manufacturing apparatuses due to its characteristics of being capable of causing a very small amount of liquid to land at a predetermined position with accuracy. For example, the liquid ejecting apparatus is applied to a display manufacturing apparatus that manufactures a color filter such as a liquid crystal display, an electrode producing apparatus that produces an electrode, such as an organic electro luminescence (EL) display or a field emission display (FED), and a chip manufacturing apparatus that manufactures a bio chip (biochemical component).
The liquid ejecting head as described above may include a flow path of a liquid that is configured to have a plurality of plate-like structural members (substrates) which are joined to each other in a stacked state. Since the liquid flow path has been formed as an extremely fine structure in accordance with a recent trend toward miniaturization of the liquid ejecting head, a silicon substrate (silicon single crystal substrate) that has crystallinity is preferably used as the structural member of the liquid flow path and thus the liquid flow path is formed with high accuracy by anisotropic etching of the substrates (for example, JP-A-2009-165932). In addition, the substrates are joined to each other by using an adhesive. At this time, when the thickness of the adhesive is formed to be great, there is a concern that the adhesive leaks into the liquid flow path side when the substrates are joined to each other. The leaked adhesive spreads along a corner or the like of the flow path and then is attached to a driving portion for performing ejection of a liquid, or the like, which adversely affects the ejection of the liquid in some cases. Therefore, it is desirable that the thickness of the adhesive be formed to be as small as possible and, for example, be 10 μm or less. This is why application of the adhesive on a joining surface of the substrate is performed by transferring (for example, see JP-A-2009-165932). Specifically, the adhesive is applied on a transferring film on a squeegee stand in a uniform thickness by using a squeegee and then the adhesive layer applied on the film is transferred to the joining surface of the substrate. Thus, it is possible to adjust the thickness of the adhesive layer on the substrate to be small. As the adhesive, for example, an epoxy adhesive, a silicon adhesive, or a urethane adhesive is used.
Incidentally, in a method using the above transferring, after a transferring film 56 on which an adhesive 55 is applied is temporarily pasted to a substrate 57 as illustrated in FIG. 7A, the transferring film 56 is detached from the substrate 57 and thereby the adhesive 55 is transferred to the substrate 57 as illustrated in FIG. 7B. Then, as illustrated in FIG. 7C, ridge portions 55a where the adhesive 55 is applied to be relatively thick and trough portions 55b where the adhesive 55 is applied to be relatively thin are formed to be alternately repeated and a phenomenon in which the thickness of the adhesive 55 is non-uniform (hereinafter, also referred to as a waviness phenomenon of the adhesive) occurs. Composition or viscosity of the adhesive 55 affects a degree of thickness differences between or repetition of the ridge portions 55a and the trough portions 55b and the waviness phenomenon may occur in any case of using the various methods of bonding described above. The exact reason of the occurrence of the waviness phenomenon is unknown, but a bonding area is likely to be relatively wide in a configuration in which a very thin adhesive is transferred to the substrate using the transferring film 56. In a case where the substrates are joined to each other in a state in which the thickness of the transferred adhesive 55 is non-uniform due to the waviness phenomenon, a joining force is insufficient at the trough portions 55b and thus joining failure occurs. As a result, a problem arises in that ink leaks between liquid flow paths in the liquid ejecting head which includes a plurality of liquid flow paths.